Biogas production from chicken manure wastes using an LBR-CSTR two-stage system: process efficiency, economic feasibility, and carbon dioxide footprint

BACKGROUND The growth of poultry farming has increased the amount of chicken manure (CM) being produced. In this study, CM was digested in a two-stage anaerobic digestion (AD) system consisting of three leach bed reactors (LBRs) and a continuous stirred tank reactor (CSTR) coupled with sedimentation tanks (anaerobic contact process). The accumulated biomass and supernatant from the sedimentation tank were returned to the CSTR and the LBRs, respectively, resulting in an almost closed (water) circuit process. In addition, zeolite was used as bulking agent and adsorbent for ammonia in the LBRs. RESULTS This study revealed that the methane yield remained on average at 0.17 NL g(-1) of Volatile Solids (VS), corresponding to the 43% of the CM biochemical methane potential as determined in separate batch tests (0.40 NL g(-1) VS). Electrical conductivity gradually increased from 22 to 26 mS cm(-1); however, the ammonia nitrogen concentration was stable at 2.28 g L-1, which was attributed to zeolite used as LBRs' bulking agent. A preliminary design of a full-scale LBR-CSTR facility was conducted for a poultry farm growing one million broilers per year. Its CO2 footprint was evaluated based on literature indices. CONCLUSION The proposed facility has a capacity of 130 kW Combined Heat and Power (CHP) and a payback period of 8.6 years. In terms of GHG emissions, implementing the LBR-CSTR system for biogas production could potentially reduce the CO2 footprint of the farm from 1.38 to 0.49 kg CO2 eq/head. (c) 2022 Society of Chemical Industry (SCI).